U.S. Pat. No. 4,569,471 to Ingemansson et al. describes a process and apparatus for feeding lengths of continuous glass fiber strands into a muffler outer shell. The apparatus includes a nozzle for expanding the fiber strands into a wool-like material before the fiber strands enter the outer shell. It has been found that the nozzle disclosed in the '471 patent is only capable of expanding strand material to a density of about 70 grams/liter or more. However, it would be desirable to expand strand material into a wool-like material which has a density of less than 70 grams/liter, for example, between about 30 grams/liter to about 60 grams/liter. Such lower density wool-type material is desirable for many sound and thermal insulation applications.